Block and tackle window balance springs are ordinarily arranged in metal channels that also contain a system of pulleys and a cord copperating with the balance spring, for counterbalancing a window sash. The spring, pulleys, and cord are preassembled into the channel and are then mounted in a window as a subassembly, ready to attach to a counterbalanced sash.
Such channel-mounted block and tackle window balance systems have encountered difficulty in anchoring one end of the spring to an end region of the channel. The spring force for these systems can be large, with a short spring travel distance that the block and tackle spreads over a longer distance, matching the vertical travel of the sash. Under such circumstances, the spring anchorage must resist several hundred pounds of force.
One way that springs have been anchored in channels, for window balance purposes, is a hook formed in a terminal coil of the spring to hook over a rivet that extends between side walls of the channel. The hook then becomes the weakest part of the spring, and the rivet between the channel walls requires a separate assembly and can also fail. Another anchorage uses cut and indented channel walls to form pockets that interlock with a spring anchoring clip, to which the spring is attached. This involves cutting and forming the channel walls in preparation for receiving the clip and also fabricating a clip in a suitable configuration.
We have discovered a simpler, less expensive, and more effective and reliable way of anchoring a counterbalance spring within a channel, for window balance purposes. Our anchor securely and reliably attached to the spring and then is made to interlock with the channel in a strong and secure way that does not required prefabricating pockets within the channel. Our anchor also accomplishes this at a lower cost than suitable alternatives.